During the transit of Venus across the Sun's face on June 5-6, 2012, the Hubble Space Telescope will be looking in the opposite direction - at the Moon. Hubble cannot look at the Sun directly, so astronomers are planning to use the Moon as a mirror to capture reflected sunlight and isolate the small fraction of the light that passes through Venus's atmosphere. Imprinted on that light are the fingerprints of the planet's atmospheric makeup. This is an experiment to see how well Venus's atmosphere can be studied spectroscopically, as a proxy for transit observations of extrasolar planets. Credit: NASA, ESA, and A. Feild (STScI)